Computational Analysis of Characteristics and Mach Number Effects on Noise Emission From Ideally Expanded Highly Supersonic Free-Jet

2007 ◽  
Author(s):  
Taku Nonomura ◽  
Kozo Fujii
Keyword(s):  
Mach Number ◽  
Stokes Equations ◽  
Acoustic Noise ◽  
Time Integration ◽  
Three Dimensional ◽  
Integration Scheme ◽  
Noise Emission ◽  
Sonic Jet ◽  
Time Integration Scheme ◽  
Seventh Order

In this study, aero-acoustic noise from super-sonic jet plume is computationally investigated. Three-dimensional Navier-Stokes equations are solved with seventh order weighted compact non-linear scheme and total validation diminishing Runge-Kutta time integration scheme. At first, the noise from Mach 2.0 ideally expanded super-sonic jet is computed and validated with the past experimental study. Then the noises from various Mach number (2.0–3.5) ideally expanded jet plumes are computed. Noise source positions, directivity and convective Mach numbers are discussed.

A Time-Accurate Projection Method for Low-Mach Number Variable Density Flows in Curvilinear Grids

2009 ◽  
Author(s):  
F. N. Fard ◽  
B. Lessani
Keyword(s):  
Mach Number ◽  
Turbulent Flows ◽  
Projection Method ◽  
Time Integration ◽  
Variable Density ◽  
Integration Scheme ◽  
Coordinate Systems ◽  
Low Mach Number ◽  
Curvilinear Coordinate ◽  
Time Integration Scheme

A time-accurate numerical algorithm is proposed for low Mach number variable density flows in curvilinear coordinate systems. In order to increase the stability of the method, a predictor-corrector time integration scheme, coupled with the projection method, is employed. The projection method results in a constant-coefficient Poisson equation for the pressure in both the predictor and corrector steps. The continuity equation is fully satisfied at each step. To prevent the pressure odd-even decoupling typically encountered in collocated grids, a flux interpolation technique is developed. The spatial discretization method offers computational simplicity and straightforward extension to 3D curvilinear coordinate systems, which are essential in the simulation of turbulent flows in complex geometries. The accuracy and stability of the algorithm are tested with a series of numerical experiments, and the results are validated against the available data in the literature.

Numerical simulation of parafoil inflation via a Robin–Neumann transmission-based approach

2017 ◽  
Vol 232 (4) ◽  
pp. 797-810 ◽  
Author(s):  
Shuai Nie ◽  
Yihua Cao ◽  
Zhenlong Wu
Keyword(s):  
Stokes Equations ◽  
Fluid Structure Interaction ◽  
Time Integration ◽  
Three Dimensional ◽  
Structural Deformation ◽  
Dimensional Case ◽  
Integration Scheme ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Highly Nonlinear

In this paper, a partitioned coupled iterative approach based on the Robin–Neumann transmission condition is proposed for the fluid–structure interaction simulation of the inflation process of a parafoil. The Reynold-averaged Navier–Stokes equations and the versatile finite element method are employed to solve the fluid flow field and the structural deformation, respectively. The generalized-α time integration scheme for the structure and the second order back Euler scheme for the fluid are incorporated in the Robin-Neumann method. A modified spring-transfinite interpolation hybrid method is exploited to detect the deformation of the grid and regenerate the grid for the fluid architecture. Both a two-dimensional case and a three-dimensional case are studied to examine the feasibility of the present approach. The simulation results reveal the evolution of the flow regime during the inflation process when the air pours into the parafoil. The whole inflation process can be concluded as two stages: the span-wise deployment and the longitudinal expansion. The numerical aerodynamic performance agrees well with that obtained by wind-tunnel experiment, suggesting the effectiveness of this method in handling such a highly nonlinear fluid–structure interaction in parachute inflation.

scholarly journals IMPACT: an implicit time integration scheme for chemical species and families

2000 ◽  
Vol 18 (3) ◽  
pp. 337-346 ◽  
Author(s):  
G. D. Carver ◽  
P. A. Stott
Keyword(s):  
Middle Atmosphere ◽  
Time Integration ◽  
Three Dimensional ◽  
Chemical Species ◽  
Atmospheric Composition ◽  
Implicit Time ◽  
Integration Scheme ◽  
Implicit Time Integration ◽  
Time Integration Scheme ◽  
Complex Chemistry

Abstract. The implicit time integration scheme of Stott and Harwood (1993) was proposed as an efficient scheme for use in three-dimensional chemical models of the atmosphere. The scheme was designed for chemistry schemes using `chemical families', in which species with short lifetimes are grouped into longer-lived families. Further study with more complex chemistry, more species and reactions showed the scheme to be non-convergent and unstable under certain conditions; particularly for the perturbed chemical scenarios of polar stratospheric winters. In this work the scheme has been improved by revising the treatment of families and the convergence properties of the scheme. The new scheme has been named IMPACT (IMPlicit Algorithm for Chemical Time-stepping). It remains easy to implement and produces simulations that compare well with integrations using more accurate higher order schemes.Key words: Atmospheric composition and structure (middle atmosphere - composition and chemistry; lioposphere - composition and chemistry; instruments and techniques)

scholarly journals Parallel graph-grammar-based algorithm for the longest-edge refinement of triangular meshes and the pollution simulations in Lesser Poland area

2021 ◽  
Author(s):  
Krzysztof Podsiadło ◽  
Albert Oliver Serra ◽  
Anna Paszyńska ◽  
Rafael Montenegro ◽  
Ian Henriksen ◽  
...  
Keyword(s):  
Time Integration ◽  
Three Dimensional ◽  
Reaction Model ◽  
Graph Grammar ◽  
Diffusion Reaction ◽  
Integration Scheme ◽  
Triangular Meshes ◽  
Time Integration Scheme ◽  
Parallel Graph ◽  
Refinement Algorithm

AbstractIn this paper, we propose parallel graph-grammar-based algorithm for the longest-edge refinements and the pollution simulations in Lesser Poland area. We introduce graph-grammar productions for Rivara’s longest-edged algorithm for the local refinement of unstructured triangular meshes. We utilize the hyper-graph to represent the computational mesh and the graph-grammar productions to express the longest-edge mesh refinement algorithm. The parallelism in the original Rivara’s longest edge refinement algorithm is obtained by processing different longest edge refinement paths in different three ads. Our graph-grammar-based algorithm allows for additional parallelization within a single longest-edge refinement path. The graph-grammar-based algorithm automatically guarantees the validity and conformity of the generated mesh; it prevents the generation of duplicated nodes and edges, elongated elements with Jacobians converging to zero, and removes all the hanging nodes automatically from the mesh. We test the algorithm on generating a surface mesh based on a topographic data of Lesser Poland area. The graph-grammar productions also generate the layers of prismatic three-dimensional elements on top of the triangular mesh, and they break each prismatic element into three tetrahedral elements. Next, we propose graph-grammar productions generating element matrices and right-hand-side vectors for each tetrahedral element. We utilize the Streamline Upwind Petrov–Galerkin (SUPG) stabilization for the pollution propagation simulations in Lesser Poland area. We use the advection–diffusion-reaction model, the Crank–Nicolson time integration scheme, and the graph-grammar-based interface to the GMRES solver.

scholarly journals An investigation of stress inaccuracies and proposed solution in the material point method

2019 ◽  
Vol 65 (2) ◽  
pp. 555-581 ◽  
Author(s):  
José Leόn González Acosta ◽  
Philip J. Vardon ◽  
Guido Remmerswaal ◽  
Michael A. Hicks
Keyword(s):  
Shape Function ◽  
Time Integration ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Material Point Method ◽  
Material Point ◽  
Point Method ◽  
Implicit Time ◽  
Integration Scheme ◽  
Time Integration Scheme

AbstractStress inaccuracies (oscillations) are one of the main problems in the material point method (MPM), especially when advanced constitutive models are used. The origins of such oscillations are a combination of poor force and stiffness integration, stress recovery inaccuracies, and cell crossing problems. These are caused mainly by the use of shape function gradients and the use of material points for integration in MPM. The most common techniques developed to reduce stress oscillations consider adapting the shape function gradients so that they are continuous at the nodes. These techniques improve MPM, but problems remain, particularly in two and three dimensional cases. In this paper, the stress inaccuracies are investigated in detail, with particular reference to an implicit time integration scheme. Three modifications to MPM are implemented, and together these are able to remove almost all of the observed oscillations.

scholarly journals Fluid/Structure Coupled Aeroelastic Computations for Transonic Flows in Turbomachinery

2002 ◽  
Author(s):  
Hirofumi Doi ◽  
Juan J. Alonso
Keyword(s):  
High Performance ◽  
Load Transfer ◽  
Time Integration ◽  
Three Dimensional ◽  
Convergence Acceleration ◽  
Integration Scheme ◽  
Fluid Structure ◽  
Flow Solver ◽  
Operational Conditions ◽  
Time Integration Scheme

The present study demonstrates the capabilities of a fluid/structure coupled computational approach which consists of an unsteady three-dimensional Navier-Stokes flow solver, TFLO, and a finite element structural analysis package, MSC/NASTRAN. The parallelized flow solver relies on a multi-block cell-centered finite volume discretization and the dual time stepping time integration scheme with multigrid for convergence acceleration. High accuracy is pursued with respect to load transfer, deformation tracking and synchronization between the two disciplines. As a result, the program successfully predicts the aeroelastic responses of a high performance fan, NASA Rotor 67, over a range of operational conditions. The results show that the unsteady pressure generated at the shock may act to damp or excite the blade motion mainly depending on the inter-blade phase angle. It is concluded that the level of sophistication in the individually sophisticated disciplines together with an accurate coupling interface will allow for accurate prediction of flutter boundaries of turbomachinery components.

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